With specific hardware configurations, Windows refuses to let you change the Critical Battery Level below a specific point. If you’ve got a big battery, this prevents you from using every last bit of juice. Thankfully, there are two easy workarounds.

We’ve already shown you How To Tweak the Low Battery Action on Your Windows 7 Laptop, but Windows can be stubborn. On my particular laptop, it won’t let me set the critical battery level to anything below 5%; it changes back to 5% as soon as I click something else. On my netbook, that’s close to 20 minutes I’m missing out on, and it takes less than 30 seconds to hibernate so I know I would be fine with 1%. Depending on your specific hardware this number may be different, or you may be lucky and not have this problem at all; it appears that many Macbooks running Windows 7 don’t have this issue. If you’re like me, however, there are two solutions you can choose from: one that’s easy and another that’s slightly more involved.

Pull the Battery

Plug in your laptop so that it’s drawing power from the wall. You can pull the battery on the live system this way without any problems. Once the battery is removed, you should be able to change the critical battery level like normal, only this time your settings won’t change back. When you’re done, just put the battery back in.

This doesn’t appear to work on all systems. If you tried this and it didn’t work, the next solution will.

Use Powercfg.exe

If your laptop doesn’t have a user-replaceable battery, or for whatever reason you can’t remove the battery while the system is on, you’re not out of hope yet. We can set the lower percentage manually using the command-line utility Powercfg.exe, so go to Start > All Programs > Accessories > Command Prompt.

First, we need the GUID of your power scheme. Input the following command:

powercfg.exe –l

That’s an ‘l’ as in “list,” which is what powercfg will do.

Your currently active power plan will be marked with an asterisk. I only ever use the first one, but if you switch power plans, you’ll need to go through this process for each one. Find the one you want to change in the list, right-click, and select “Mark.” Now you can select the long alphanumeric string with your mouse cursor, and then hit the Enter key to copy it. You should paste this in a notepad window, because we’ve got more to copy.

Next, we need the GUID of the subgroup and the setting we’re looking to change. Run the following command and replace “[SCHEME_GUID]” with what you just copied.

powercfg.exe –q [SCHEME_GUID]

You’ll get a low of text in the command prompt. Scroll through it and look for “Critical battery level.” First you need to copy the long alphanumeric string that belongs to the subgroup “Battery,” which you can find a short ways above “Critical battery level.” Paste that in your notepad window. You’ll next need to copy the GUID for the setting, which is right next to “Critical Battery level.” The following screenshot highlights the section to look for in red and the two GUIDs you need to copy in cyan.

Fill in the Scheme, Subgroup, and Setting GUIDS from your notepad window and replace “[VALUE]” with your desired percentage. Hit the Enter key to set it. Here’s the command I used for my particular needs:

This will set my critical battery level when on battery power to 1%. If you want to also change the setting for when you’re on AC power as well, just hit the Up key in the command prompt (to bring up your previous command) and change the

-setdcvalueindex

option to:

-setacvalueindex

That’s it! Now you can squeeze every last possible minute out of your battery, whether Windows wants you to or not!